The present invention relates to slide type press machine. More specifically, the present invention provides for a press machine having a slide that moves linearly in a vertical direction through the use of a toggle link. The present invention is useful when the stroke-length for a slide needs to be changed with a large change ratio or when the bottom dead center needs to be adjusted.
An example of a press machine that provides linear vertical motion of a slide is found in Japanese examined patent publication number 7-55399. This press provides linear vertical motion of a slide by converting the rotation of an eccentric section of a crank shaft to a linear reciprocating motion. The linear reciprocating motion is transferred, via a connecting link, to a central connecting pin which connects an upper and lower toggle link. In this example, the rotation of the eccentric section of the crank shaft is converted to the linear reciprocating motion of a slider via a connecting piece. The slide and the central connecting pin are connected on either side of a first link and a second link. This provides for vertical motion of the slide. An externally threaded screw connects a third link and a fourth link. The third and fourth links for a parallelogram with the first and second links. The externally threaded screw is used to adjust vertical positioning, thus adjusting the stroke-length and the bottom dead center of the slide.
In Japanese laid-open patent publication number 48-42471, there is disclosed a stroke-length adjustment mechanism where an eccentric shaft is fixed with a lock pin so that the stroke-length can be changed in two stages.
Another press machine is disclosed in Japanese examined patent publication number 7-55399. In this press machine, the vertical motion of the externally threaded screw provides adjustment by changing the shape of the first link through the fourth link, which form a parallelogram. Increasing the adjustment length of the externally threaded screw provides only a small change ratio for the slide stroke-length of about 4. With the change in the slide stroke-length, there is also a large displacement in the bottom dead center. Thus, even if fine adjustments of the bottom dead center are possible for a specific stroke-length, the change ratio of the stroke-length will be small. Thus, a restriction is imposed on the height of the die.
In presses that use toggle links, there is generally high acceleration at the point of reversal at the bottom dead center of the slide. This makes high-speed operation difficult.
A stroke-length adjustment mechanism in a press machine is disclosed in Japanese laid-open patent publication number 48-42471. This conventional stroke-length adjustment mechanisms cannot be changed continuously. In the press disclosed in Japanese examined patent publication number 7-55399, the stroke-length can be changed continuously by using a screw mechanism in the stroke-length adjustment mechanism. However, in this case, the press load will be applied to the screw mechanism during press operation, requiring the screw mechanism to have a sturdy structure. The device must be made larger in order to provide a sturdy structure, resulting in increased production costs.
It is an object of the present invention is to provide a press machine which overcomes the problems of the prior art.
It is another object of the present invention to provide a press machine having a compact design.
It is yet another object of the present invention to provide a press machine having a slide with an adjustable stroke-length.
It is still another object of the present invention to provide for a press machine having an adjustable bottom dead center position.
It is an object of the present invention to provide a press machine that has a large change ratio for the slide stroke-length, allows fine adjustments of the bottom dead center, and uses a toggle link having a low acceleration at the bottom dead center to raise and lower the slide.
It is a further object of the present invention to provide a press machine where the stroke-length can be changed continuously, reducing the press load applied to the screw mechanism used in the stroke-length adjusting mechanism, thus permitting a compact design.
Briefly stated, a pressing machine has a stroke length adjustment mechanism in which: changing of the stroke length does not effect the bottom dead center position of the press, adjustment is simplified, and the press is suitable for high speed pressing operations. The slide-type pressing machine has an eccentric section of a crank shaft which causes a slider to move up and down. An arm extends past a fixed pivot of an upper toggle link. One end of the arm is connected to the slider by a connecting link. A drive link and a drive connecting link are connected by a connecting pivot. A worm wheel is disposed on a frame, and is concentric with the connecting pivot when the slide is at bottom dead center. The worm wheel is arranged so that its rotation angle can be adjusted. A second arm is disposed in a radial direction from the axis of the worm wheel. A second pin is located at an end of the second arm. The second pin is connected to the connecting pivot via a third link. The motion of the connecting pivot is restricted to either an arcuate or linear path. The position of the second pin is changed to adjust the stroke length of the slide and the bottom dead center is kept fixed.
According to an embodiment of the invention, there is provided for a press including a slider, the slider being driven to move vertically from rotation of a crank shaft via a connecting rod, a drive link connected to one end of the slider, an upper toggle link pivotably supported at one point by a fixed pivot, connected at one end to the drive connecting link, and connected at another end to a slide via a link member, and a stroke adjusting mechanism restricting a pivoting motion of a pivot connecting the drive link and the drive connecting link. This embodiment of the invention can provide: a larger change ratio for the stroke-length than found in conventional press machines, an adjustable die height, and the stroke-length can be adjusted while leaving the bottom dead center unchanged. Thus, fine adjustments to the bottom dead center, known as bottom dead center correction, can be performed while the press is operating. Machine vibration is reduced since there is no extreme increase in acceleration at the top dead center, thus allowing the use of this invention in presses that require high-speed operation. Since a certain amount of space can be provided between the link members connecting the crank shaft and the slide, the design of the pitch between points is more flexible.
Furthermore, by changing the position of the pivot connecting the drive link and the drive connecting link when the press is at top dead center, a xe2x80x9cquick liftxe2x80x9d feature is made available for the press. A quick lift feature is a feature for presses with short stroke-lengths wherein the slide can be temporarily raised for maintenance of the die or the like. Then the distance between dies can be increased. Once maintenance is complete, the original die height can be restored.
According to another embodiment of the invention, there is provided for a press machine having a stroke-length adjusting mechanism including a connecting pivot projected from a drive link, a third link connected at one end to the connecting pivot, a shaft pivotably supported by a frame, a second arm fixed at one end to the shaft and connected at another end to another end of the third link, and means for rotating the shaft. This embodiment of the invention provides for a press that has a simple structure and that includes a stroke-length adjusting mechanism with reduced production costs compared to conventional technology.
According to yet another embodiment of the invention, there is provide for a press machine having means for rotating a shaft, the means for rotating including a worm wheel fixed to the shaft, and a worm shaft meshing with the worm wheel. With this embodiment, stroke-length adjustments can be performed continuously and a more compact means for rotating the shaft is possible.
According to an embodiment of the invention, there is provide for a press machine a stroke-length adjusting mechanism which has means for fixing a shaft, the means for fixing including: a fixing cylinder movably fitting with the shaft, a jaw disposed on the shaft restricting a displacement distance of the fixing cylinder, and means for supplying pressurized oil to the jaw and the fixing cylinder. With this embodiment of the invention, the shaft connected to the rotating means can be fixed, reducing the effect that press loads generate on the rotating means during pressing operation.
According to another embodiment of the invention, there is provided for a press machine having a stroke-length adjusting mechanism, the stroke-length adjusting mechanism including: a pin projecting from a drive link, a gear on which is disposed a guide groove in which is movably fitted the pin, and means for adjusting gear angle for adjusting a rotation angle of the gear. With this invention, the stroke-length can be determined by the rotation angle of the gear, i.e., the rotation angle of the guide groove. Thus, a stroke-length adjusting mechanism can be provided with reduced production costs.
According to the present invention, there is provided for a press comprising: a slider, the slider is moveable along a vertical axis, a crank shaft, a connecting rod, the connecting rod couples a rotation of the crank shaft to the slider such that the slider moves along the vertical axis in response to a rotation of the crank shaft, a drive link, the drive link having one end, the one end of the drive link is coupled to the slider, a drive connecting link, the drive connecting link having one end, the one end of the drive connecting link is coupled to the drive link, an upper toggle link, the upper toggle link having one end and another end, a fixed pivot, the upper toggle link is pivotably supported at one point by the fixed pivot, the one end of the upper toggle link is coupled to the drive connecting link, a link member, the another end of the upper toggle link is coupled to the slide via the link member, and a stroke length adjusting mechanism restricting a pivoting motion of a pivot connecting the drive link and the drive connecting link.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.